I propose to continue our studies of neural mechanisms of pain perception and pain inhibition in the rat. We will focus our attention on the midbrain central gray matter but will also study the spinal cord and the raphe nuclei. A recurrent theme is to compare the mechanisms underlying analgesia from brain stimulation with those underlying analgesia from opiate drugs. In another type of study, we propose to investigate aversive areas of the brain. My overall objective in the proposed research is to identify the neural systems involved in pain appreciation and especially pain inhibition. We hope that advances can be made in our basic understanding of these problems and that this progress will lead to important clinical applications. Brain stimulation, lesion, and electrophysiological recording techniques will be applied. Pharmacological manipulations and behavioral testing procedures will also be employed.